/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.neo4j.cypher.internal.util

object Ref {
  def apply[T <: AnyRef](v: T) = new Ref[T](v)

  def unapply[T <: AnyRef](v: Ref[T]): Option[T] = Some(v.value)
}

final class Ref[+T <: AnyRef](val value: T) {

  if (value == null)
    throw new IllegalArgumentException("Attempt to instantiate Ref(null)")

  /**
   * A unique id of this ref, as given by System.identityHashCode.
   */
  def id: Int = java.lang.System.identityHashCode(value)

  def toIdString: String = Integer.toHexString(id)

  override def toString = s"Ref@$toIdString($value)"

  override def hashCode: Int = id

  override def equals(that: Any): Boolean = that match {
    case other: Ref[_] => value eq other.value
    case _             => false
  }
}
